Engine starter motor control for preventing damage during hydraulic lock

ABSTRACT

A locomotive diesel engine starter motor control including a power supply, starter contacts and a parallel circuit comprised of a normally open contacter and an impedance series coupled with the starter motor. A circuit is provided for opening and closing the contacter so as to periodically insert the impedance in series with the starter motor as a function of starter motor speed to regulate the speed and the torque applied to the engine to a specified limit for a time duration that insures that the engine is rotated at least one revolution with the torque applied thereto being insufficient to rotate the engine through a hydraulic lock. After the time duration, the contacter is maintained closed to allow the starting motor to crank the engine at full speed at maximum applied torque.

'United States Patent [19] Chen [ Dec. 16, 1975 [75] Inventor: Stephen S. Chen, Downers Grove,

Ill.

[73] Assignee: General Motors Corporation,

Detroit, Mich.

22 Filed: Nov. 15, 1973 21 Appl. No.: 415,977

[44] Published under the Trial Voluntary Protest Program on January 28, 1975 as document no.

12/1970 Safiuddin 318/434 9/l97l Welsh 290/38 R Primary ExaminerRobert K. Schaefer Assistant ExaminerW. E. Duncanson, Jr. Attorney, Agent, or Firm l'loward N. Conkey 57 ABSTRACT A locomotive diesel engine starter motor control including a power supply, starter contacts and a parallel circuit comprised of a normally open contacter and an impedance series coupled with the starter motor. A Circuit is provided for opening and closing the contacter so as to periodically insert the impedance in series with the starter motor as a function of starter motor speed to regulate the speed and the torque applied to the engine to a specified limit for a time duration that insures that the engine is rotated at least one revolution with the torque applied thereto being insufficient to rotate the engine through a hydraulic lock. After the time duration, the contacter is maintained closed to allow the starting motor to crank the engine at full speed at maximum applied torque.

2 Claims, 2 Drawing Figures [52] US. Cl. 318/434; 290/38 R [51] Int. Cl. H02? 7/14 [58] Field of Search 290/28, 38, DIG. l, DIG.'l 1; 318/434 56] References Cited UNITED STATES PATENTS 2925.810 2/l960 Mendenhall 290/38 R X 3.469.106 9/1969 Seilly 290/38 R W z? I a fPC SWATCH yp TIMER CKT. 4

SENSOR US. Patent Dec. 16, 1975 ENGINE STARTER MOTOR CONTROIJ'EOR PREVENTING DAMAGE DURING HYDRAULIC LOCK This invention relates to a starter motor control for a locomotive dieselengine and more specifically, to such a control for limiting the speed of the starter motor for at least one revolution of the engine tolimit the torque applied thereto to a level insufficient for rotating the engine through a hydraulic lock. I

When a diesel engine with aleak in a power assembly is shut down for an extended period of time, a significant amount of liquid can be accumulated in the cylinder head exhaust passage of the. cylinder if the piston is abovejthe cylinder air inlet ports. I

In the case of water accumulation in the cylinder head, when the engine is rotated to start and the piston moves to the bottom of its stroke to expose the cylinder air inlet ports to the cylinder, the water is released into the cylinder by the opening of the exhaust valves; Although a portion of this water can escape into the air box through the air inlet ports when the piston is at'the bottom of its stroke, some is trapped above the piston on its upward stroke. This is especially true when the engine is'being rotated at a high rate.

In the case of water or fuel being accumulated in the cylinder and the piston is moving toward the bottom of its stroke, a fast cranking engine will not allow sufficient time for all of this liquid to escape through the air inlet ports when thepiston terminates its downward stroke and some will be trapped by the upward movement of the piston.

In the case of water or fuel being accumulated. in the cylinder and the piston is in its upward stroke, there is no means for the liquid to escape from the cylinder and consequently will be trapped by the upward movement of the piston.

In any of the above cases, when the engine is rotated until the volume between the cylinder head and the piston head is filled with fluid, the engine experiences what will hereinafter be termed a hydraulic lock, i.e., the cylinder cannot be moved any further due to the incompressibility of the fluid. If sufficient torque is applied for rotating the engine, damage will generally result to the combustion gasket, connecting rod or result in a cracked carrier or piston. When the locomotive engine is cranked by the starter motor delivering full starting torque, suffic-ient torque is applied to the locomotive engine such that if a cylinder experiences a hydraulic lock, the aforementioned damage can occur.

The general object of this invention is to provide a locomotive diesel engine starter motor control for preventing damage to the engine during an engine hydrauliclock.

It is another object of this invention toprovide a locomotive engine starter motor control wherein the speed of the starter motor is monitored upon initiating the starting of the locomotive engine and is thereafter regulated for a predetermined timeperiod representing at least one complete revolution of the locomotive engine to a speed wherein the torque applied to the locomotive engine is below the torque required to rotate the engine through a hydraulic lock and thereby prevent damage thereto. e v x i The invention may be best understood by reference to the following description of a preferred embodiment and the drawings wherein: 3

, ing thepreferredembodiment of this invention for limiting the outputtorque. of the starter motor to prevent rotation of the locomotive engine through a hydraulic lock; and

FIG. 2 is a schematic drawing of the switch and timer circuit of FIG. 1.3:

Referring toFIG. 1, a locomotive diesel engine is cranked-by -a conventional locomotive engine starter motor assembly generally designated by the numeral 10 which includes a. pair of starter motors M-1 and M--2 havingrespective output drive shafts 12 and 14. Each of the output driveshafts l2 and 14 terminates in the usual pinion gear (not shown) which, during engine cranking, is positioned to engage the diesel engine ring gear.

The starter motor M-l has associated therewith a low resistance pickup coil 16 anda high resistance hold in coil 18 which'are operatively associated with a conventional starter motor solenoid plunger (not shown) which drives the pinion gear coupled to the output shaft 12 to engage the diesel engine ring gear when the pickup coil 16 is energized and holds them in engagement when the hold in coil 18 is energized. In like manner, the-starter motor M-2 has associated therewith a low resistance pickup coil 20 and a high resistance hold in coil 22 which are operatively associated with a solenoid plunger (not shown) which drives the pinion gear coupled to the output shaft 14 to engage diesel engine ring gear and hold them in engagement in the same manner as the pickup coil 16 and the hold in coil 18.

The starter motors M-1 and M-2 are electrically coupled in series as are the pickup coil 16, thehold in coil 18, the hold in coil 22 and the pickup coil 20, the two series circuits being coupled in parallel.

A pair of normally opened contacters 24 and26 are mechanically associated with the movement'of the solenoid plungers which are operated by the pickup coils l6 and 20 in the conventional manner such that the contacter 24 is closed when the pinion gear on the output shaft 12 is engaged with the ring gear of the diesel engine and the contacter 26 is closed when the pinion gear on the output shaft 14 is positioned into engagement with the diesel engine ring gear. The contacter 24 has one side thereof coupled between the pickup coil 16 and the hold in coil 18 and the other side coupled to one side of a main starting coil GSA. The other side of the main starting coil GSA is coupled to one side of the contacter 26, the other side of which is coupled between the pickup coil 20 and the hold in coil 22.

The main starting coil GSA has associated therewith a pair of normally open contacters GSA-l and GSA-2 which-are closed .upon the energization of the main starter coil GSA.

Power for energizing the starter motors M-1 and M-2 is provided by a DC battery 28 whose positive terminal is coupled to a battery switch 30 which is closed by the locomotive operator when the locomotive is being operated.

Anormally openstarter switch 32 is series coupled with an engine starting coil GS, this series circuit being coupled in parallel with the series coupled battery 28 and battery switch 30. The engine starting coil GS has associated therewith a pair of normally open starting contacter s GS-l and GS-2 which are closed upon the energization of the starting coil GS. One side of the contacter GS -.1 is coupled to the positive terminal of 3 battery 28 through the battery switch 30 and the other side coupled between the pickup coil 16 and the hold in coil 18. One side of the contacter GS-2 is coupled to the negative terminal of the DC battery 28 and the other side thereof coupled between the pickup coil 20 and the hold in coil 22.

Thepositive terminal of the DC battery 28 is coupled to one side of the series coupled starter motors M-1 and M-2 through the battery switch 30, a parallel combination of a normally opened contacter EPC-1 and a-resistor 34, a fuse 36, the normally opened contacter GSA-1 and a low resistance shunt 38. The negative terminal of the DC battery is coupled to the other side of the series coupled starter motors M-1 and M-2 through the normally opened contacter GSA-2.

The cranking speed of the starter motors M-1 and M-2 is monitored by a current sensor 40 in conjunction with the shunt 38 and a pair of resistors 42 and 44 which are series coupled from the high voltage side of the shunt 38 across the starter motors M-1 and M2. The junction between the resistors 42 and 44 is coupled to one side of an input coil 46 of the current sensor 40, the other side of which is coupled to the low voltage side of the shunt 38. The voltage drop across the shunt 38 is directly proportional to the current through the starter motors M-1 and M-2 and the voltage 'at the junction of the resistors 42 and 44 is directly proportional to the voltage applied across the starter motors M-1 and M-2. Consequently, the current through the coil 46 has a magnitude determined by the voltage across and current through the starter motors M-1 and M-2. As the cranking speed of the starter motors M-1 and M-2 is a direct function of this voltage and current, the current through the coil 46 is a direct measurement of the cranking speed.

The current sensor 40 includes an output NPN transistor 48 whose emitter and collector electrodes is directly coupled to a switch and timer circuit 50. Regulated power is applied to the switch and timer circuit 50 and the current sensor 40 by means of a series circuit comprised of a current limiting resistor 51, a Zener diode 54 and the contacter GSA-2 coupled across the DC battery 28 through the battery switch 30. As can be seen, upon the closure of the contacter GSA-2, the switch and timer circuit 50 and the current sensor 40 are enabled, i.e., power is at that time coupled across the current sensor 40 and the switch and timer circuit 50 from the cathode of the Zener diode 54 and through the contacter GSA-2. A coil EPC is coupled between the switch and timer circuit 50 and the battery switch 30.

The current sensor 40 may take the form of the Magsense Comparator, Part No. 70 E 7001, manufactured by Pioneer Instrumentation Division of Pioneer-Standard Electronics, Inc, 4,800 East 131st Street, Cleveland, Ohio. For use with the subject starter motor control, the output of the above Magsense Comparator is taken directly across the collector and emitter electrodes of the output transistor thereof, this transistor being designated by numeral 48 in FIG. I.

The current sensor 40 is responsive to the current through the input coil 46 thereof and functions to bias the output transistor 48 thereof into conduction when the magnitude of the current through the'input coil 46 represents a speed of the starter motors M-1 and M-2 which exceeds a specified speed at which the torque applied for rotating the locomotive diesel engine is insufficient for rotating the engine through a hydraulic lock. When the speed of the starting motor M-1 and M-2 decreases below the specified speed, the current sensor 40 is responsive to the resulting current through the input coil 46 to bias the transistor 48 into non-conduction.

The switch and timer circuit 50 is responsive to the state of the output transistor 48 in the current sensor 40 for energizing the coil EPC to close the contacter EPC-l when the transistor 48 is biased into non-com duction, and for deenergizing the coil EPC to open the contacter EPC-1 when the transistor 48 is biased into conduction. The switch and timer circuit 50 is further operative for maintaining the coil EPC energized after a predetermined time duration following the enabling of the switch and timer circuit 50 upon the closure of the contacter GSA-2. This time duration is equivalent to the time required to rotate the locomotive diesel engine at least one complete revolution by the starter motors M-1 and M-2 when operating at the aforementioned specified speed at which insufficient torque is applied to rotate the diesel engine through a hydraulic lock.

Referring to FIGS. 1 and 2, the switch portion of the switch and timer circuit 50 includes a Darlington amplifier 52 comprised of an NPN transistor 54 and an NPN transistor 56. The collector electrode of the transistor 54 is coupled to the positive terminal of the DC battery 28 through a resistor 58 and the battery switch 30. The collector electrode of the transistor 56 is coupled to one side of the coil EPC and the emitter electrode is coupled to the negative terminal of the DC battery 28 through the contacter GSA-2. The positive terminal of the DC battery 28 is coupled to the base electrode of the transistor 54 through the battery switch 30, a resistor 60 and a Zener diode 62, the anode of the Zener diode 62 being coupled to the'base electrode of the transistor 54. The cathode of the Zener diode 62 is coupled to the negative terminal of the DC battery 28 through a resistor 64, a capacitor 66 and the contacter GSA-2. The collector of the transistor 56 is also coupled to ground through a Zener diode 68.

The timer portion of the switch and timer circuit 50 includes a resistor 70 and a capacitor 72 coupled in series across the Zener diode 54. The junction between the resistor 70 and the capacitor 72 is coupled to the base electrode of a PNP transistor 74 through a diode 76. The base electrode of the transistor 74 is coupled to the negative terminal of the DC battery 28 through a resistor 78 and the contacter GSA-2'. A voltage divider comprised of a resistor 80 and a resistor 82 is coupled across the Zener diode 54 with the junction between said resistors being coupled to the emitter electrode of the transistor 74. The collector electrode-of the transistor 74 is coupled to the base of an N-PN transistor 84 through a resistor 86. The emitter electrode of the transistor 84 is coupled to the negative terminal of the DC battery 28 through the contacter GSA-2.

The emitter electrode of the output transistor 48 of the current sensor 46 is coupled to the collector electrode of the transistor 84 and the collector electrode of the output transistor 48 is coupled to the "cathode of the Zener diode 62.

The operation of the subject invention will be described with reference to FIGS. 1 and 2. When it is desired to operate the locomotive, the locomotive operator closes the battery switch 30 to supply power from the battery 28 to various locations in the locomotive including the subject circuit. Thereafter, to start the locomotive engine, the operator closes the starter switch 32 to energize the engine starting coil GS. Energization of the coil GS operates to close the contacters GS-l and GS-2 to energize the pickup coils l6 and through the starter motors M-land M- 2 which effects the engagement of the pinion gears coupled to the output shafts l2 and 14 and the diesel engine ring gear as previously described. At that time, contacters 24 .and 26 are closed as previously described to complete an energizing path for the main starter coil GSA. Also, the

hold in coils 18 and 22 are energized to maintain engagement of the pinion gears and ring gear.

Upon the energization of the main starter coil GSA, the normally open contacters GSA-l and GSA-2 are closed. Closure of the contacters GSA-1 and GSA-2 completes the energization path for the starter motors M-1 and M-2 through either the resistor 34 or the contacter EPC-1 and, further, closure of the contacter GSA-2 enables the current sensor 40 and the switch and timer circuit 50. The current sensor 46 then monitors the speed of the starter motors M-1 and M-2 as previously described. When theswitch and timer circuit 50'is enabled by the closure of the contacter GSA- 2, the base electrode of the transistor 74 is at the potential of the negative terminal of the DC battery 28. Consequently, the transistor 74 is biased into conduction to bias the transistor 84 into conduction. Also upon closure of the contacter GSA-2, the capacitor 72 begins to charge through the resistor 70 at a controlled rate.

The speed of the starter motors M-l andM-2 upon the initial energization thereof is below the specified speed at which the torque applied to rotate the diesel engine is insufficient to rotate the engine through a hydraulic lock. Consequently, the output transistor 48 of the current sensor 40 is biased into non-conduction as previously described. The capacitor 66 is then charged through the resistor 60 and the resistor 64 and, after a delayed time, the Darlington amplifier 52 is biased into conduction to energize the coil EPC to close the contacter EPC-1. Consequently, the voltage of the DC battery 28 is applied directly across the starter motors M-1 and M-2 which accelerate toward the maximum speed. When the starter motors M-1 and M-2 exceed the specified speed, the output transistor 48 in the current sensor 40 is biased into conduction to couple the base electrode of the transistor 54 to ground through the transistor 84, which is conducting as previously described, to deenergize the Darlington amplifier 52 and consequently the coil EPC to effect the opening of the contacter EPC-l. The resistor 34 is then coupled in series with the starter motors M-1 and M-2. As aresult of the decreased power supplied thereto, the starter motors M-1 and M-2 decelerate toward a speed determined by the value of the resistor 34 which is below the specified speed. When the speed of the starter motors M-1 and M-2 decrease below the specified speed, the output transistor 48 in the current sensor 46 again is biased into non-conduction. Assuming the engine does not experience a hydraulic lock, the cycle is continually repeated so as to regulate the speed of the starter motors M-1 and M-2 at the specified speed until the capacitor 72, which is being charged through the resistor 70 at the predetermined rate, charges to a level to bias the transistor 74 into non-conduction which in turn biases the transistor 84 into non-conduction. The time constant of the resistor 70 and the capacitor 72 is such that the capacitor 72 charges to the level to bias the transistor 74 into non-conduction after the specified time durationwhich ensures that the diesel engine has been cranked one complete revolution. When the transistor 84 is biased into non-conduction, the ground pathfor the transistor 48 in the current sensor 46 is removed to prevent the transistor 48 from biasing the Darlington amplifier 52 into non-conduction. Thereafter, the Darlingtonamplifier 52 is continually biased into conduction to .maintain the coil EPC energized and the-contacter EPC-1- closed to apply the voltage of the DC battery 28 directly across the starter motors M-1 and M-2 which rotate at maximum speed and apply maximum torque for rotating the locomotive diesel engine to effect the starting thereof.

If a cylinder of the diesel engine contained fluid which would cause a hydraulic lock, such a lock would occur during the revolution the engine was cranked at or below the specified speed. As the torque output of the starter motors M-1 and M-2 during this time is insufficient to rotate the diesel engine through the hydraulic lock, they would stall. Power to the starter motors M-1 and M-2 would then be removed by the locomotive operator by opening the starter switch 32 or by the blowing of the fuse 36 by the current surge resulting from the stall.

Although the speed of the starter motors M-1 and M-2 while cranking the engine through the first revolution is generally insufficient to start the engine, the 10- comotive. operator may disable the fuel supply to the engine to ensure that it will not start until the engine is cranked at the maximum speed.

Summarizing, the speed of the starter motors M-1 and M-2 are controlled at aspecified level for the predetermined time duration which insures that the locomotive engine is rotated through at least a single revolution with an applied torque insufficient to rotate the engine through a hydraulic lock. If a cylinder contained fluid such as would cause a hydraulic lock, this insures that the starter motors would not rotate the engine through the hydraulic lock .but would stall and thereby prevent damage to the engine. If a cylinder did not contain fluid which would cause a hydraulic lock, after the engine was rotated through at least the single revolution, the starter motors M-1 and M-2 would then operate at maximum speed with maximum applied torque to effect the starting of the locomotive engine.

The preferred embodiment of the invention illustrates the cranking of the locomotive engine by a pair of starter motors for illustration purposes only. It is understood that a single or an. additional number of starter motors can be used;

The detailed description of the preferred embodiment of the invention for the purpose of explaining the principles thereof is not to be considered as limiting or restricting the invention, since many modifications may be made by the exercise of skill in the art without departing from the scope of the invention.

What is claimed is:

1. A starter motor control for preventing damage to an engine when said engine experiences a hydraulic lock due to fluid contained in a cylinder thereof, comprising: a DC power source; a starter motor effective for cranking the engine; means for coupling the DC power source to the starter motor to effect cranking of the engine, said means including a parallel circuit comprised of a contacter and an impedance, the DC power source being coupled directly to the starter motor when the contacter is closed so as to-crank the engine at maximum speed with maximum applied torque and being speed of the starter motor; means responsive to the signal for closing the contacter when the speed of the starter motor is less than the specified speed and opening the contacter when the speed is greater than the specified speed; and timer means for preventing the last mentioned means from opening the contacter after a specified time duration following the coupling of the DC power source to the starter motor, said time duration being at least equal to the time required for the starter motor when operating at the specified speed to rotate the engine through one complete revolution, whereby the starter motor cranks the engine at or below the specified speed for the specified time duration with an applied torque insufficient to rotate the engine when said engine experiences a hydraulic lock.

2. An engine starter motor control for preventing damage to an engine when said engine experiences a hydraulic lock due to fluid contained in a cylinder thereof, comprising: a starter motor effective for cranking the engine; a starter motor energizing circuit including a DC power source, a parallel circuit comprised of an impedance and a speed control contacter, and a starter contacter series coupled with the starter motor, the starter motor being coupled directly to the DC power source when the starter contacter and the speed control contacter are closed so as to crank the engine at =maximum speed with maximum applied torque and being coupled to the DC power source through the starter contacter and the impedance when the speed control contacter is opened so as to crank the engine at a rate belowa specified speed at which the applied torque is insufficient to rotate the engine when said engine experiences a hydraulic lock; means for generating a'first signal directly related to the magnitude of current through the starter motor; means for generating a second signal directly related to the magnitude of the voltage across the starter motor; means responsive to the first and second signals for generating a third signal having a magnitude directly related to the speed of the starter motor; means responsive to the third signal for closing the contacter when the magnitude of said signal represents a speed of the starter motor less than specified speed and opening the contacter when the speed is greater than the specified speed; and timer means for disabling the last mentioned means from opening the contacter when the speed of the starter motor is greater than the specified speed after a predetermined time duration from the closing of the starter contacter, said time duration being at least equal to the time required for the starter motor when operating at the specified speed to rotate the engine through one complete revolution, whereby the starter motor cranks the engine at or below the specified speed for the specified time duration with an applied torque insufficient to rotate the engine when said engine experiences a hydraulic lock. 

1. A starter motor control for preventing damage to an engine when said engine experiences a hydraulic lock due to fluid contained in a cylinder thereof, comprising: a DC power source; a starter motor effective for cranking the engine; means for coupling the DC power source to the starter motor to effect cranking of the engine, said means including a parallel circuit comprised of a contacter and an impedance, the DC power source being coupled directly to the starter motor when the contacter is closed so as to crank the engine at maximum speed with maximum applied torque and being coupled to the starter motor through the impedance when the contacter is opened so as to crank the engine at a speed below a specified speed at which the applied torque is insufficient to rotate the engine when said engine experiences a hydraulic lock; means for generating a signal having a magnitude directly related to the speed of the starter motor; means responsive to the signal for closing the contacter when the speed of the starter motor is less than the specified speed and opening the contacter when the speed is greater than the specified speed; and timer means for preventing the last mentioned means from opening the contacter after a specified time duration following the coupling of the DC power source to the starter motor, said time duration being at least equal to the time required for the starter motor when operating at the specified speed to rotate the engine through one complete revolution, whereby the starter motor cranks the engine at or below the specified speed for the specified time duration with an applied torque insufficient to rotate the engine when said engine experiences a hydraulic lock.
 2. An engine starter motor control for preventing damage to an engine when said engine experiences a hydraulic lock due to fluid contained in a cylinder thereof, comprising: a starter motor effective for cranking the engine; a starter motor energizing circuit including a DC power source, a parallel circuit comprised of an impedance and a speed control contacter, and a starter contacter series coupled with the starter motor, the starter motor being coupled directly to the DC power source when the starter contacter and the speed control contacter are closed so as to crank the engine at maximum speed with maximum applied torque and being coupled to the DC power source through the starter contacter and the impedance when the speed control contacter is opened so as to crank the engine at a rate below a specified speed at which the applied torque is insufficient to rotate the engine when said engine experiences a hydraulic lock; means for generating a first signal directly related to the magnitude of current through the starter motor; means for generating a second signal directly related to the magnitude of the voltage across the starter motor; means responsive to the first and second signals for generating a third signal having a magnitude directly related to the speed of the starter motor; means responsive to the third signal for closing the contacter when the magnitude of said signal represents a speed of the starter motor less than specified speed and opening the contacter when the speed is greater than the specified speed; and timer means for disabling the last mentioned means from opening the contacter when the speed of the starter motor is greater than the specified speed after a predetermined time duration from the closing of the starter contacter, said time duration being at least equal to the time required for the starter motor when operating at the specified speed to rotate the engine through one complete revolution, whereby the starter motor cranks the engine at or below the specified speed for the specified time duration with an applied torque insufficient to rotate the engine when said engine experiences a hydraulic lock. 